Merge Issue.pyi back to source (#2568)

Co-authored-by: Enrico Minack <github@enrico.minack.dev>

github/GithubObject.py

@@ -46,15 +46,15 @@ from typing import (
     Any,
     Callable,
     Dict,
-    Generic,
     List,
     Optional,
+    Tuple,
     Type,
     Union,
 )
 
 from dateutil import parser
-from typing_extensions import TypeGuard
+from typing_extensions import Protocol, TypeGuard
 
 from . import Consts
 from .GithubException import BadAttributeException, IncompletableObject
@@ -63,15 +63,16 @@ if TYPE_CHECKING:
     from .Requester import Requester
 
 T = typing.TypeVar("T")
+T_co = typing.TypeVar("T_co", covariant=True)
 
 
-class Attribute(Generic[T]):
+class Attribute(Protocol[T_co]):
     @property
-    def value(self) -> T:
+    def value(self) -> T_co:
         raise NotImplementedError
 
 
-class _NotSetType(Attribute):
+class _NotSetType:
     def __repr__(self):
         return "NotSet"
 
@@ -97,15 +98,15 @@ def is_defined(v: Union[T, _NotSetType]) -> TypeGuard[T]:
     return not isinstance(v, _NotSetType)
 
 
-def is_undefined(v: Any) -> TypeGuard[_NotSetType]:
+def is_undefined(v: Union[T, _NotSetType]) -> TypeGuard[_NotSetType]:
     return isinstance(v, _NotSetType)
 
 
-def is_optional(v, type: Type[T]) -> TypeGuard[Opt[T]]:
+def is_optional(v, type: Union[Type, Tuple[Type, ...]]) -> bool:
     return isinstance(v, _NotSetType) or isinstance(v, type)
 
 
-def is_optional_list(v, type: Type[T]) -> TypeGuard[Opt[List[T]]]:
+def is_optional_list(v, type: Union[Type, Tuple[Type, ...]]) -> bool:
     return (
         isinstance(v, _NotSetType)
         or isinstance(v, list)
@@ -113,7 +114,7 @@ def is_optional_list(v, type: Type[T]) -> TypeGuard[Opt[List[T]]]:
     )
 
 
-class _ValuedAttribute(Attribute, Generic[T]):
+class _ValuedAttribute(Attribute[T]):
     def __init__(self, value: T):
         self._value = value